Alkali-free glass

ABSTRACT

An alkali free glass has an average coefficient of thermal expansion at 50 to 350° C. of 30×10 −7  to 43×10 −7 /° C., a Young&#39;s modulus of 88 GPa or more, a strain point of 650 to 725° C., a temperature T 4  at which a viscosity reaches 10 4  dPa·s of 1,290° C. or lower, a glass surface devitrification temperature (T c ) of T 4 +20° C. or lower, and a temperature T 2  at which the viscosity reaches 10 2  dPa·s of 1,680° C. or lower. The alkali free glass contains, as represented by mol % based on oxides, 62 to 67% of SiO 2 , 12.5 to 16.5% of Al 2 O 3 , 0 to 3% of B 2 O 3 , 8 to 13% of MgO, 6 to 12% of CaO, 0.5 to 4% of SrO, and 0 to 0.5% of BaO. MgO+CaO+SrO+BaO is 18 to 22%, and MgO/CaO is 0.8 to 1.33.

TECHNICAL FIELD

The present invention relates to an alkali free glass suitable as aglass substrate for various displays, photomasks, electronic devicesupports, information recording media, planar antennas, etc.

BACKGROUND ART

A glass to be used as a glass sheet (glass substrate) for variousdisplays, photomasks, electronic device supports, information recordingmedia, planar antennas, etc., particularly a glass to be used as a glasssheet on which a thin film of metal, oxide or the like should be formedon its surface is required to have the following characteristics (1) to(4) and so on.

(1) When the glass contains alkali metal oxide, the glass should containsubstantially no alkali metal ion that may be diffused into the thinfilm to thereby deteriorate the film properties of the thin film.

(2) The glass should have a strain point high enough to minimizedeformation of the glass sheet and contraction (thermal contraction)caused by structural stabilization of the glass when the glass sheet isexposed to high temperature in a step of forming the thin film.(3) The glass should have enough chemical durability against variouschemicals used for forming a semiconductor. Particularly the glassshould have durability against alkali such as buffered hydrofluoric acid(BHF: liquid mixture of hydrofluoric acid and ammonium fluoride) usedfor etching SiO_(x) or SiN_(x), chemical liquid containing hydrochloricacid used for etching ITO, various acids (such as nitric acid, sulfuricacid, etc.) used for etching metal electrodes, and alkali of resistpeeling liquid.(4) The glass should have no defects (bubbles, striae, inclusions, pits,scratches, etc.) inside the glass and in the surface of the glass.

In addition to the aforementioned requirements, the followingcharacteristics are also required in recent years.

(5) The glass should have a small specific weight due to a request toreduce the weight of a display.

(6) The glass sheet should be thinned due to the request to reduce theweight of the display.

(7) The glass should have heat resistance to manufacture a polycrystalsilicon (p-Si) type liquid crystal display high in heat treatmenttemperature as well as a conventional amorphous silicon (a-Si) typeliquid crystal display (heat treatment temperature of a-Si: about 350°C., heat treatment temperature of p-Si: 350 to 550° C.).(8) The glass should have a small average coefficient of thermalexpansion in order to increase a temperature increase/increase rate inthermal treatment for manufacturing the liquid crystal display tothereby increase the productivity or to increase the thermal shockresistance. On the other hand, when the average coefficient of thermalexpansion of the glass is too small, the number of steps of formingvarious films such as a gate metal film and a gate insulating film inmanufacturing of the liquid crystal display may increase to increase thewarpage of the glass. Thus, defects such as cracks or scratches mayoccur when the liquid crystal display is being conveyed, causing aproblem such as increase in misalignment of an exposure pattern.(9) The glass should have a high specific elastic modulus (Young'smodulus/density) in accordance with increase in size and reduction insheet thickness of the glass substrate.

In order to satisfy the aforementioned requirements, various glasscompositions have been, for example, proposed in glasses for liquidcrystal display panels (see Patent Literatures 1 to 4).

CITATION LIST Patent Literature

Patent Literature 1: Japanese Patent No. 5702888

Patent Literature 2: WO 2013/183626

Patent Literature 3: Japanese Patent No. 5849965

Patent Literature 4: Japanese Patent No. 5712922

SUMMARY OF INVENTION Technical Problem

Resolution has been made higher and higher in recent electronicdisplays. In a large-sized television, for example, film thickness of Cuwiring has increased in accordance with higher definition thereof. Forsuch a reason, warpage in a substrate tends to increase due to formationof various films. Therefore, to answer increasing needs for substrateswith reduced warpage, it is necessary to increase the Young's modulus ofa glass.

However, a known glass having a high Young's modulus as described inPatent Literature 3 or 4 has a high strain point and tends to have ahigh devitrification temperature as compared with a temperature T₄ atwhich viscosity reaches 10⁴ dPa·s. As a result, the glass cannot beformed easily, so that a load on manufacturing facilities increases.Thus, there is concern that the production cost may increase.

An object of the present invention is to provide a glass capable ofinhibiting deformation such as warpage in a glass substrate, excellentin formability, and low in load on manufacturing facilities.

Solution to Problem

In order to attain the foregoing object, an alkali free glass accordingto the present invention has an average coefficient of thermal expansionat 50 to 350° C. of 30×10⁻⁷ to 43×10⁻⁷/° C., a Young's modulus of 88 GPaor more, a strain point of 650 to 725° C., a temperature T₄ at whichviscosity reaches 10⁴ dPa·s of 1,290° C. or lower, a glass surfacedevitrification temperature (T_(c)) of T₄+20° C. or lower, and atemperature T₂ of 1,680° C. or lower at which the viscosity reaches 10²dPa·s, and contains, as represented by mol % based on oxides,

62 to 67% of SiO₂,

12.5 to 16.5% of Al₂O₃,

0 to 3% of B₂O₃,

8 to 13% of MgO,

6 to 12% of CaO,

0.5 to 4% of SrO, and

0 to 0.5% of BaO,

wherein MgO+CaO+SrO+BaO is 18 to 22%, and MgO/CaO is 0.8 to 1.33.

In another configuration of the alkali free glass according to thepresent invention, specific elastic modulus may be 34 MN·m/kg or higher.

In another configuration of the alkali free glass according to thepresent invention, density may be 2.60 g/cm³ or lower.

In another configuration of the alkali free glass according to thepresent invention, glass surface devitrification viscosity (η_(c)) maybe 10^(3.8) dPa·s or higher.

In another configuration of the alkali free glass according to thepresent invention, a glass transition temperature may be 730 to 790° C.

In another configuration of the alkali free glass according to thepresent invention, a value expressed by the following Expression (I) maybe 4.10 or more.(7.87[Al₂O₃]−8.5[B₂O₃]+11.35[MgO]+7.09[CaO]+5.52[SrO]−1.45[BaO])/[SiO₂]  Expression (I)

In another configuration of the alkali free glass according to thepresent invention, a value expressed by the following Expression (II)may be 0.95 or more.(−1.02[Al₂O₃]+10.79[B₂O₃]+2.84[MgO]+4.12[CaO]+5.19[SrO]+3.16[BaO])/[SiO₂]  Expression (II)

In another configuration of the alkali free glass according to thepresent invention, a value expressed by the following Expression (III)may be 5.5 or less.(8.9[Al₂O₃]+4.26[B₂O₃]+11.3[MgO]+4.54[CaO]+0.1[SrO]−9.98[BaO])×{1+([MgO]/[CaO]−1)²}/[SiO₂]  Expression(III)

In another configuration of the alkali free glass according to thepresent invention, the glass may contain 0.5% or lower of SnO₂ asrepresented by mol % based on oxides.

In another configuration of the alkali free glass according to thepresent invention, a β-OH value may be 0.05 to 0.5 mm⁻¹.

In another configuration of the alkali free glass according to thepresent invention, compaction may be 100 ppm or lower.

In another configuration of the alkali free glass according to thepresent invention, an equivalent cooling rate may be 5 to 500° C./min.

In another configuration of the alkali free glass according to thepresent invention, the glass may be a glass sheet having at least oneside of 1,800 mm or longer and a thickness of 0.7 mm or less.

In another configuration of the alkali free glass according to thepresent invention, the glass may be manufactured by a float process or afusion process.

In addition, a display panel according to the present invention includesan alkali free glass according to the present invention.

In addition, a semiconductor device according to the present inventionincludes an alkali free glass according to the present invention.

In addition, an information recording medium according to the presentinvention includes an alkali free glass according to the presentinvention.

In addition, a planar antenna according to the present inventionincludes an alkali free glass according to the present invention.

Advantageous Effects of Invention

According to the present invention, it is possible to provide a glasscapable of inhibiting deformation such as warpage in a glass substrate,excellent in formability, and low in load on manufacturing facilities.

DESCRIPTION OF EMBODIMENT

An embodiment of the present invention is described below. The presentinvention is not limited to the embodiment which is described below.

In the following description, a composition range of each component of aglass is expressed by mol % based on oxides.

In the following description, a numerical range expressed by “numericalvalue A to numerical value B” designates a range including the numericalvalue A and the numerical value B as a minimum value and a maximum valueof the range respectively, and means that the range is not less than thenumerical value A and not more than the numerical value B.

First, a composition of an alkali free glass according to the embodimentis described.

When the content of SiO₂ is lower than 62 mol % (hereinafter referred toas % simply), there is a tendency that the strain point of the glassdoes not increase sufficiently while the average coefficient of thermalexpansion thereof increases and the specific weight thereof increases.Therefore, the content of SiO₂ is 62% or higher, preferably 62.5% orhigher, more preferably 63% or higher, particularly preferably 63.5% orhigher, and most preferably 64% or higher.

When the content of SiO₂ exceeds 67%, there is a tendency that themeltability of the glass decreases and the Young's modulus thereofdecreases while the devitrification temperature thereof increases.Therefore, the content of SiO₂ is 67% or lower, preferably 66.5% orlower, more preferably 66% or lower, and particularly preferably 65.7%or lower.

Al₂O₃ increases the Young's modulus to inhibit deflection, inhibitsphase separation of the glass, and improves a fracture toughness valueto increase glass strength. When the content of Al₂O₃ is lower than12.5%, those effects do not appear easily. In addition, other componentsincreasing the average coefficient of thermal expansion increaserelatively. As a result, the average coefficient of thermal expansiontends to increase. Therefore, the content of Al₂O₃ is 12.5% or higher,preferably 12.8% or higher, and more preferably 13% or higher.

When the content of Al₂O₃ exceeds 16.5%, the meltability of the glassdeteriorates, the strain point increases, and the devitrificationtemperature may increase. Therefore, the content of Al₂O₃ is 16.5% orlower, preferably 16% or lower, more preferably 15.7% or lower, evenmore preferably 15% or lower, particularly preferably 14.5% or lower,and most preferably 14% or lower.

B₂O₃ is not an essential component. However, B₂O₃ improves resistance toBHF, improves melting reaction of the glass and decreases thedevitrification temperature. Therefore, B₂O₃ may be contained by 3% orlower. The content of B₂O₃ is 3% or lower, preferably 2.5% or lower,more preferably 2.2% or lower, even more preferably 2% or lower,particularly preferably 1.7% or lower, and most preferably 1.5% orlower.

MgO increases the Young's modulus without increasing the specificweight, so that MgO can increase the specific elastic modulus to therebyinhibit deflection. In addition, MgO improves the fracture toughnessvalue to increase the glass strength. Further, MgO also improves themeltability. When the content of MgO is lower than 8%, those effects donot appear easily. In addition, the coefficient of thermal expansion maybe too low. Therefore, the content of MgO is 8% or higher, preferably8.2% or higher, and more preferably 8.5% or higher.

On the contrary, when the content of MgO is too high, thedevitrification temperature tends to increase. Therefore, the content ofMgO is 13% or lower, preferably 12% or lower, more preferably 11% orlower, even more preferably 10.5% or lower, particularly preferably 10%or lower, and most preferably 9.7% or lower.

CaO is characterized by increasing the specific elastic modulus next toMgO among alkali earth metals, and preventing the strain point fromdecreasing excessively. CaO also improves the meltability in the samemanner as MgO. Further, CaO is also characterized by making thedevitrification temperature not higher than MgO does. When the contentof CaO is lower than 6%, those effects do not appear easily. Therefore,the content of CaO is 6% or higher, preferably 7% or higher, morepreferably 8% or higher, and even more preferably 9% or higher.

When the content of CaO exceeds 12%, the average coefficient of thermalexpansion becomes too high, and the devitrification temperatureincreases to devitrify the glass easily during the manufacturing of theglass. Therefore, the content of CaO is 12% or lower, preferably 11% orlower, and more preferably 10% or lower.

SrO improves the meltability without increasing the devitrificationtemperature of the glass. However, when the content of SrO is lower than0.5%, those effects do not appear easily. Therefore, the content of SrOis 0.5% or higher, preferably 1% or higher, more preferably 1.2% orhigher, and even more preferably 1.5% or higher.

The aforementioned effects in SrO are lower than those in BaO. When thecontent of SrO increases excessively, an effect of increasing thespecific weight surpasses those effects, and the average coefficient ofthermal expansion may also increase excessively. Therefore, the contentof SrO is 4% or lower, preferably 3% or lower, more preferably 2.5% orlower, and even more preferably 2% or lower.

BaO is not an essential component. However, BaO improves the meltabilitywithout increasing the devitrification temperature of the glass.Therefore, BaO may be contained in the alkali free glass of theembodiment. However, when the content of BaO is excessive, there is atendency that the specific weight increases, the Young's modulusdecreases, and the average coefficient of thermal expansion increasesexcessively. Therefore, the content of BaO is 0.5% or lower. Morepreferably in the glass in the embodiment, BaO is substantially notcontained.

The phrase “substantially not contained” designates that a component isnot contained but as impurities mixed from raw materials or the like,that is, not contained intentionally. In the embodiment, when BaO issubstantially not contained, the content of BaO is, for example, 0.3% orlower, preferably 0.2% or lower, more preferably 0.1% or lower, evenmore preferably 0.05% or lower, and particularly preferably 0.01% orless.

When the total content of alkali earth metal oxides, that is,MgO+CaO+SrO+BaO (hereinafter also referred to as “RO”) is low, thedevitrification temperature increases, that is, the devitrificationviscosity decreases, so that formability deteriorates. Therefore, RO isset at 18% or higher.

When RO is too rich, the average coefficient of thermal expansion mayincrease, and resistance to acid deteriorates. Therefore, RO is 22% orlower, preferably 21.5% or lower, more preferably 21% or lower, evenmore preferably 20.7% or lower, particularly preferably 20.5% or lower,and most preferably 20.3% or lower.

A small proportion of the MgO content to the CaO content, that is, asmall ratio MgO/CaO accelerates precipitation of CaO—Al₂O₃—SiO₂ basedcrystals to thereby deteriorate the formability. Specifically, thedevitrification temperature increases, that is, the devitrificationviscosity decreases. Therefore, MgO/CaO is 0.8 or higher, preferably0.85 or higher, more preferably 0.9 or higher, and even more preferably0.92 or higher. However, when MgO/CaO is too high, MgO—Al₂O₃—SiO₂ basedcrystals are precipitated easily so that the devitrification temperatureincreases, that is, the devitrification viscosity decreases. Therefore,MgO/CaO is 1.33 or lower, preferably 1.3 or lower, more preferably 1.25or lower, even more preferably 1.2% or lower, particularly preferably1.1% or lower, most preferably 1.05% or lower.

Alkali metal oxides such as Li₂O, Na₂O and K₂O are substantially notcontained in the alkali free glass according to the embodiment. Whenalkali metal oxides are substantially not contained in the embodiment,the total content of the alkali metal oxides is, for example, 0.5% orlower, preferably 0.2% or lower, more preferably 0.1% or lower, furthermore preferably 0.08% or lower, even more preferably 0.05% or lower, andmost preferably 0.03% or lower.

When an alkali free glass sheet is used for manufacturing a display, itis preferable that P₂O₅ is substantially not contained in the alkalifree glass according to the present invention, in order to preventdeterioration in properties of a thin film of metal, oxide or the likeprovided on the surface of the glass sheet. In the embodiment, when P₂O₅is substantially not contained, the content of P₂O₅ is, for example,0.1% or lower. Further, in order to recycle the glass easily, it ispreferable that PbO, As₂O₃ and Sb₂O₃ are substantially not contained inthe alkali free glass according to the embodiment. In the embodiment,when PbO, As₂O₃ and Sb₂O₃ are substantially not contained, the contentof each of PbO, As₂O₃ and Sb₂O₃ is, for example, 0.01% or lower, andpreferably 0.005% or lower.

In order to improve the meltability, refining property, formability,etc. of the glass, the alkali free glass according to the embodiment maycontain one or more kinds of ZrO₂, ZnO, Fe₂O₃, SO₃, F, Cl and SnO₂ by 2%or lower, preferably 1% or lower, and more preferably 0.5% or lower intotal. F is a component which improves the meltability and refiningproperty of the glass. When F is contained in the alkali free glassaccording to the embodiment, the content of F is preferably 1.5% orlower (0.43 mass % or lower). SnO₂ is a component which also improvesthe meltability and refining property of the glass. When SnO₂ iscontained in the alkali free glass according to the embodiment, thecontent of SnO₂ is preferably 0.5% or lower (1.1 mass % or lower).

A β-OH value of the alkali free glass according to the present inventionis preferably 0.05 to 0.5 mm⁻¹.

The β-OH value is an index of the amount of moisture contained in theglass. For a glass sample, absorbance against a light of a wavelength of2.75 to 2.95 μm is measured, and a maximum value β_(max) of the measuredabsorbance is divided by the thickness (mm) of the sample. Thus, theβ-OH value is obtained. When the β-OH value is 0.5 mm⁻¹ or lower,compaction that is described later can be attained easily. The β-OHvalue is more preferably 0.45 mm⁻¹ or lower, more preferably 0.4 mm⁻¹ orlower, further more preferably 0.35 mm⁻¹ or lower, even more preferably0.3 mm⁻¹ or lower, particularly preferably 0.28 mm⁻¹ or lower, and mostpreferably 0.25 mm⁻¹ or lower. On the other hand, when the β-OH value is0.05 mm⁻¹ or higher, a strain point of a glass which is described latercan be attained easily. The β-OH value is more preferably 0.08 mm⁻¹ orhigher, further more preferably 0.1 mm⁻¹ or higher, even more preferably0.13 mm⁻¹ or higher, particularly preferably 0.15 mm⁻¹ or higher, andmost preferably 0.18 mm⁻¹ or higher.

In the alkali free glass according to the embodiment, a value expressedby the following Expression (I) is preferably 4.10 or more.(7.87[Al₂O₃]−8.5[B₂O₃]+11.35[MgO]+7.09[CaO]+5.52[SrO]−1.45[BaO])/[SiO₂]  Expression(I)

The value expressed by Expression (I) is an index of the Young'smodulus. When the value is less than 4.10, the Young's modulus isreduced. In the alkali free glass according to the embodiment, the valueexpressed by Expression (I) is more preferably 4.15 or more, even morepreferably 4.2 or more, particularly preferably 4.25 or more, and mostpreferably 4.3 or more.

In the aforementioned Expression (I), [Al₂O₃], [B₂O₃], [MgO], [CaO],[SrO], [BaO] and [SiO₂] represent the contents of Al₂O₃, B₂O₃, MgO, CaO,SrO, BaO and SiO₂ as represented by mol % based on oxides, respectively.The same thing can be applied to the following Expressions (II) and(III).

In the alkali free glass according to the embodiment, a value expressedby the following Expression (II) is preferably 0.95 or more.(−1.02[Al₂O₃]+10.79[B₂O₃]+2.84[MgO]+4.12[CaO]+5.19[SrO]+3.16[BaO])/[SiO₂]  Expression (II)

The value expressed by Expression (II) is an index of the strain point.When the value is less than 0.95, the strain point is increased. In thealkali free glass according to the embodiment, the value expressed byExpression (II) is more preferably 1.0 or more, even more preferably1.05 or more, and particularly preferably 1.1 or more.

In the alkali free glass according to the embodiment, a value expressedby the following Expression (III) is preferably 5.5 or less.(8.9[Al₂O₃]+4.26[B₂O₃]+11.3[MgO]+4.54[CaO]+0.1[SrO]−9.98[BaO])×{1+([MgO]/[CaO]−1)²}/[SiO₂]  Expression(III)

The value expressed by Expression (III) is an index of the glass surfacedevitrification viscosity (η_(c)). When the value exceeds 5.5, the glasssurface devitrification viscosity (η_(c)) is reduced. In the alkali freeglass according to the embodiment, the value expressed by Expression(III) is more preferably 5.1 or less, even more preferably 4.8 or less,particularly preferably 4.5 or less, and most preferably 4.3 or less.

In the alkali free glass according to the embodiment, the averagecoefficient of thermal expansion at 50 to 350° C. is 30×10⁻⁷/° C. orhigher. For example, in manufacturing of a TFT-side substrate of a flatpanel display, a gate metal film of copper or the like and a gateinsulating film of silicon nitride or the like may be laminatedsequentially on the alkali free glass substrate. In this case, when theaverage coefficient of thermal expansion at 50 to 350° C. is lower than30×10⁻⁷/° C., the difference in thermal expansion between the glass andthe gate metal film of copper or the like formed on the surface of thesubstrate increases so that there may arise such a problem that thesubstrate is warped or the film is separated.

The average coefficient of thermal expansion at 50 to 350° C. ispreferably 33×10⁻⁷/° C. or higher, more preferably 35×10⁻⁷/° C. orhigher, even more preferably 36×10⁻⁷/° C. or higher, particularlypreferably 37×10⁻⁷/° C. or higher, and most preferably 38×10⁻⁷/° C. orhigher.

On the other hand, when the average coefficient of thermal expansion at50 to 350° C. is higher than 43×10⁻⁷/° C., the glass may be cracked in astep of manufacturing a product such as a display. Therefore, theaverage coefficient of thermal expansion at 50 to 350° C. is 43×10⁻⁷/°C. or lower.

The average coefficient of thermal expansion at 50 to 350° C. ispreferably 42×10⁻⁷/° C. or lower, more preferably 41.5×10⁻⁷/° C. orlower, even more preferably 41×10⁻⁷/° C. or lower, particularlypreferably 40.5×10⁻⁷/° C. or lower, and most preferably 40.3×10⁻⁷/° C.or lower.

The Young's modulus of the alkali free glass according to the embodimentis 88 GPa or more. Consequently, deformation of a substrate caused byexternal stress can be inhibited. For example, warpage of the substrateis inhibited when deposited on the surface of the glass substrate. As aspecific example, in manufacturing of a TFT-side substrate of a flatpanel display, the substrate can be inhibited from warping when a gatemetal film of copper or the like or a gate insulating film of siliconnitride or the like is formed on the surface of the substrate. Forexample, deflection of the substrate when the substrate increases insize can be also inhibited. The Young's modulus is preferably 88.5 GPaor more, more preferably 89 GPa or more, even more preferably 89.5 GPaor more, particularly preferably 90 GPa or more, and most preferably90.5 GPa or more. The Young's modulus can be measured by an ultrasonicmethod.

The strain point of the alkali free glass according to the embodiment is650 to 725° C. When the strain point is lower than 650° C., a glasssheet exposed to high temperature in a step of forming a thin film on adisplay tends to be deformed and contracted (thermally contracted) dueto structural stabilization of the glass. The strain point is preferably685° C. or higher, more preferably 690° C. or higher, even morepreferably 693° C. or higher, particularly preferably 695° C. or higher,and most preferably 698° C. or higher. On the other hand, when thestrain point is too high, it is necessary to increase the temperature ofa slow cooling apparatus in accordance with the strain point. Thus, thelife of the slow cooling apparatus tends to be reduced. The strain pointis preferably 723° C. or lower, more preferably 720° C. or lower, evenmore preferably 718° C. or lower, particularly preferably 716° C. orlower, and most preferably 714° C. or lower.

In the alkali free glass according to the embodiment, a temperature T₄at which the viscosity reaches 10⁴ dPa·s is 1,290° C. or lower.Consequently, the alkali free glass according to the embodiment isexcellent in formability. In addition, for example, the temperature atwhich the glass according to the embodiment is formed can be decreasedso that volatile components in the atmosphere around the glass can bereduced to thereby reduce defects. Further, since the glass can beformed at a low temperature, a load on manufacturing facilities can bereduced. For example, the life of a float bath or the like for formingthe glass can be elongated so that productivity can be improved. T₄ ispreferably 1,287° C. or lower, more preferably 1,285° C. or lower, evenmore preferably 1,283° C. or lower, and particularly preferably 1,280°C. or lower.

T₄ can be obtained as a temperature at which viscosity measured by useof a rotary viscometer reaches 10⁴ dPa·s according to a method specifiedunder ASTM C 965-96. In Examples which are described later, NBS710 andNIST717a were used as reference samples for calibration of apparatus.

In the alkali free glass according to the embodiment, a glass surfacedevitrification temperature (T_(c)) is T₄+20° C. or lower. Consequently,the glass alkali free according to the embodiment is excellent informability. In addition, transmittance can be inhibited from decreasingdue to crystals generated inside the glass during forming. In addition,a load on manufacturing facilities can be reduced. For example, the lifeof a float bath or the like for forming the glass can be elongated sothat productivity can be improved.

The glass surface devitrification temperature (T_(c)) is preferablyT₄+10° C. or lower, more preferably T₄+5° C. or lower, even morepreferably T₄° C. or lower, particularly preferably T₄−1° C. or lower,and most preferably T₄−5° C. or lower.

The glass surface devitrification temperature (T_(c)) and a glassinternal devitrification temperature (T_(d)) can be obtained as follows.That is, crushed glass particles are put into a dish made of platinum,and a heat treatment is performed thereon for 17 hours in an electricfurnace controlled to a fixed temperature. After the heat treatment, amaximum temperature at which crystals are precipitated on the surface ofthe glass and a minimum temperature at which no crystals areprecipitated likewise are measured by use of an optical microscope, andan average of those temperatures is regarded as the glass surfacedevitrification temperature (T_(c)). In the same manner, a maximumtemperature at which crystals are precipitated inside the glass and aminimum temperature at which no crystals are precipitated likewise aremeasured, and an average of those temperatures is regarded as the glassinternal devitrification temperature (T_(d)). Viscosity in each of theglass surface devitrification temperature (T_(c)) and a glass internaldevitrification temperature (T_(d)) can be obtained by viscosity of theglass measured at the devitrification temperature.

The specific elastic modulus (Young's modulus (GPa)/density (g/cm³) ofthe alkali free glass according to the embodiment is preferably 34MN·m/kg or higher. Consequently the glass has a reduced deflection byits own weight so that the glass can be handled easily even if it isformed into a large-sized substrate. The specific elastic modulus ismore preferably 34.5 MN·m/kg or higher, even more preferably 34.8MN·m/kg or higher, particularly preferably 35 MN·m/kg or higher, andmost preferably 35.2 MN·m/kg or higher. The large-sized substrate is,for example, a substrate having at least one side of 1,800 mm or longer.At least one side of the large-sized substrate may be 2,000 mm orlonger, or 2,500 mm or longer, 3,000 mm or longer, or 3,500 mm orlonger.

The density of the alkali free glass according to the embodiment ispreferably 2.60 g/cm³ or lower. Consequently, the glass has a reduceddeflection by its own weight so that the glass can be handled easilyeven if it is formed into a large-sized substrate. In addition, a deviceusing the alkali free glass according to the embodiment can be reducedin weight. The density is more preferably 2.59 g/cm³ or lower, even morepreferably 2.58 g/cm³ or lower, particularly preferably 2.57 g/cm³ orlower, and most preferably 2.56 g/cm³ or lower.

In the alkali free glass according to the embodiment, glass surfacedevitrification viscosity (η_(c)) which is viscosity at the glasssurface devitrification temperature (T_(c)) is preferably 10^(3.8) dPa·sor higher. Consequently the glass is excellent in formability into aglass sheet. In addition, transmittance can be inhibited from decreasingdue to crystals generated inside the glass during forming. In addition,a load on manufacturing facilities can be reduced. For example, the lifeof a float bath or the like for forming the glass can be elongated sothat productivity can be improved. The glass surface devitrificationviscosity (η_(c)) is more preferably 10^(3.85) dPa·s or higher, evenmore preferably 10^(3.9) dPa·s or higher, particularly preferably 10⁴dPa·s or higher, and most preferably 10^(4.05) dPa·s or higher,

A temperature T₂ at which the viscosity of the glass according to theembodiment reaches 10² dPa·s is preferably 1,680° C. or lower.Consequently the glass is excellent in meltability. In addition, a loadon manufacturing facilities can be reduced. For example, the life of afurnace or the like for melting the glass can be elongated so thatproductivity can be improved. In addition, defects (such as spot defectsor Zr defects) caused by the furnace can be reduced. T₂ is morepreferably 1,670° C. or lower, even more preferably 1,660° C. or lower,particularly preferably 1,640° C. or lower, particularly preferably1,635° C. or lower, and most preferably 1,625° C. or lower.

A glass transition temperature of the alkali free glass according to theembodiment is preferably 730 to 790° C. When the glass transitiontemperature is 730° C. or higher, the glass is excellent in formability.For example, a deviation in sheet thickness or waving in the surface canbe reduced. On the other hand, when the strain point is 790° C. orlower, a load on manufacturing facilities can be reduced. For example, asurface temperature of a roll used for forming the glass can be reducedso that the life of facilities can be elongated, and the productivitycan be improved. The glass transition temperature is more preferably740° C. or higher, even more preferably 745° C. or higher, particularlypreferably 750° C. or higher, and most preferably 755° C. or higher. Onthe other hand, the glass transition temperature is more preferably 785°C. or lower, even more preferably 783° C. or lower, particularlypreferably 780° C. or lower, and most preferably 775° C. or lower.

In the alkali free glass according to the embodiment, compaction ispreferably 100 ppm or lower, more preferably 90 ppm or lower, furthermore preferably 80 ppm or lower, even more preferably 75 ppm or lower,particularly preferably 70 ppm or lower, and most preferably 65 ppm orlower. The compaction is a glass thermal shrinkage generated byrelaxation of a glass structure during a heat treatment. When thecompaction is 100 ppm or lower, deformation of the glass and adimensional change caused by structural stabilization of the glass canbe suppressed and minimized when the glass is exposed to hightemperature in a thin film forming step carried out in a process ofmanufacturing various displays.

The compaction in the embodiment means compaction measured in thefollowing procedure.

A glass sheet sample (sample mirror-finished with cerium oxide andmeasuring 100 mm in length, 10 mm in width and 1 mm in thickness)obtained by processing the alkali free glass according to the embodimentis retained at a temperature of the glass transition temperature +120°C. for 5 minutes, and then cooled down to room temperature at a rate of40° C. per minute. After the glass sheet sample has been cooled down tothe room temperature, total length (lengthwise) L1 of the sample ismeasured. After that, the glass sheet sample is heated to 600° C. at arate of 100° C. per hour, retained at 600° C. for 80 minutes, and cooleddown to the room temperature at a rate of 100° C. per hour. After theglass sheet sample has been cooled down to the room temperature, totallength L2 of the sample is measured again. A ratio (L1−L2)/L1 of adifference (L1−L2) in total length between before and after the heattreatment at 600° C. to the total length L1 of the sample before theheat treatment at 600° C. is regarded as a value of compaction.

In the alkali free glass according to the embodiment, for example, anequivalent cooling rate is set preferably at 500° C./min or lower inorder to reduce the compaction. The equivalent cooling rate ispreferably 5° C./min or higher and 500° C./min or lower in terms ofbalance between the compaction and the productivity. In terms of theproductivity, the equivalent cooling rate is more preferably 10° C./minor higher, even more preferably 15° C./min or higher, particularlypreferably 20° C./min or higher, and most preferably 25° C./min orhigher. In terms of the compaction, the equivalent cooling rate is morepreferably 300° C./min or lower, even more preferably 200° C./min orlower, particularly preferably 150° C./min or lower, and most preferably100° C./min or lower.

The equivalent cooling rate in the embodiment means an equivalentcooling rate measured in the following procedure.

The alkali free glass according to the embodiment is processed to obtaina plurality of samples for creating a calibration curve. Each sample hasa rectangular parallelepiped shape measuring 10 mm by 10 mm by 1 mm. Thesamples prepared thus are retained for 5 minutes at the glass transitiontemperature +120° C. by use of an infrared heating electric furnace.After that, each sample is cooled down to 25° C. at a different coolingrate ranging from 1° C./min to 1,000° C./min. Next, a refractive indexn_(d) on d-line (wavelength 587.6 nm) is measured in each sample by aV-block method using a precision refractometer KPR-2000 made by ShimadzuDevice Corporation. The value n_(d) obtained in each sample is plottedfor a logarithm of the cooling rate thereof. In this manner, acalibration curve of n_(d) for the cooling rate is obtained.

Next, the alkali free glass according to the embodiment is processedinto a rectangular parallelepiped shape measuring 10 mm by 10 mm by 1mm, and n_(d) is measured by the V-block method using the precisionrefractometer KPR-2000 made by Shimadzu Device Corporation. A coolingrate corresponding to the obtained n_(d) is acquired from thecalibration curve. The obtained cooling rate is regarded as theequivalent cooling rate.

The alkali free glass according to the embodiment has a high Young'smodulus of 88 GPa or higher to thereby inhibit deformation of asubstrate caused by external stress. Thus, the glass is suitable for aglass sheet to be used as a large-sized substrate. The large-sizedsubstrate is, for example, a glass sheet having at least one side of1,800 mm or longer. As a specific example, the substrate is a glasssheet which is 1,800 mm or longer in long sides and 1,500 mm or longerin short sides.

The alkali free glass according to the embodiment is used preferably asa glass sheet which has at least one side of 2,400 mm or longer, forexample, which is 2,400 mm or longer in long sides and 2,100 mm orlonger in short sides, more preferably as a glass sheet which has atleast one side of 3,000 mm or longer, for example, which is 3,000 mm orlonger in long sides and 2,800 mm or longer in short sides, particularlypreferably as a glass sheet which has at least one side of 3,200 mm orlonger, for example, which is 3,200 mm or longer in long sides and 2,900mm or longer in short sides, and most preferably as a glass sheet whichhas at least one side of 3,300 mm or longer, for example, which is 3,300mm or longer in long sides and 2,950 mm or longer in short sides.

The alkali free glass according to the embodiment is preferably 0.7 mmor less in thickness in terms of reduction in weight. The thickness ofthe alkali free glass according to the embodiment is more preferably0.65 mm or less, even more preferably 0.55 mm or less, particularlypreferably 0.45 mm or less, and most preferably 0.4 mm or less. Althoughthe thickness may be set at 0.1 mm or less or 0.05 mm or less, thethickness is preferably 0.1 mm or more and more preferably 0.2 mm ormore in terms of prevention of deflection by its own weight.

The alkali free glass according to the embodiment can be, for example,manufactured in the following procedure.

Raw materials for the glass are prepared to have an intended glasscomposition, thrown into a melting furnace, and heated to 1,500 to1,800° C. to be thereby melted. Thus, a molten glass is obtained. Theobtained molten glass is formed into a glass ribbon with a predeterminedsheet thickness by a forming apparatus. The glass ribbon is graduallycooled down, and then cut. Thus, the alkali free glass is obtained.

In the manufacturing of the alkali free glass according to theembodiment, it is preferable that the glass is, for example, cooled downto set the equivalent cooling rate at 500° C./min or lower in order toreduce the compaction.

In the manufacturing of the alkali free glass according to theembodiment, it is preferable that the molten glass is formed into aglass sheet by a float process, a fusion process or the like. The floatprocess is preferred in order to stably produce a large-sized sheetglass (for example, having one side of 1,800 mm or longer) with a highYoung's modulus.

Next, a display panel according to the embodiment is described.

The display panel according to the embodiment includes theaforementioned alkali free glass according to the embodiment as a glasssubstrate. The display panel is not particularly limited as long as itincludes the alkali free glass according to the embodiment. The displaypanel may be one of various display panels such as a liquid crystaldisplay panel, an organic EL display panel, etc.

Description is made in a case of a thin film transistor liquid crystaldisplay (TFT-LCD) by way of example. A gate electrode line and a gateinsulating oxide layer are formed on the surface of the display. Adisplay surface electrode substrate (array substrate) where pixelelectrodes are formed and a color filter substrate where RGB colorfilters and opposed electrodes are formed are provided on the surface ofthe oxide layer. A liquid crystal material is put between the arraysubstrate and the color filter substrate which are paired. In thismanner, a cell is constituted. A liquid crystal display panel includesnot only the cell but also other elements such as a peripheral circuitand so on. In the liquid crystal display panel according to theembodiment, the alkali free glass according to the embodiment is used asat least one of the paired substrates constituting the cell.

The alkali free glass according to the embodiment can be used as a glasssheet for supporting an electronic device. When the alkali free glassaccording to the embodiment is used as a glass sheet for supporting anelectronic device, a device forming substrate such as a glass substrate,a silicon substrate or a resin substrate is laminated on the alkali freeglass (glass sheet for supporting an electronic device) according to theembodiment directly or by use of a bonding material so that the deviceforming substrate can be supported. Examples of the glass sheet forsupporting an electronic device include a supporting glass sheet in aprocess of manufacturing a flexible display (such as an organic ELdisplay) using resin such as polyimide as a substrate, and a glass sheetfor supporting a resin-silicon chip composite wafer in a process ofmanufacturing a semiconductor package.

Next, a semiconductor device according to the embodiment is described.

The semiconductor device according to the embodiment includes theaforementioned alkali free glass according to the embodiment as a glasssubstrate. Specifically the semiconductor device according to theembodiment includes the alkali free glass according to the embodiment asa glass substrate for an image sensor such as MEMS, CMOS or CIS. Thesemiconductor device according to the embodiment includes the alkalifree glass according to the embodiment as a cover glass for a displaydevice for a projection application, such as a cover glass for LCOS(Liquid Crystal On Silicon).

Next, an information recording medium according to the embodiment isdescribed.

The information recording medium according to the embodiment includesthe aforementioned alkali free glass according to the embodiment as aglass substrate. Specifically, examples of the information recordingmedium include a magnetic recording medium, an optical disk, etc.Examples of the magnetic recording medium include an energy-assistedmagnetic recording medium and a vertical magnetic recording typemagnetic recording medium.

Next, a planar antenna according to the embodiment is described.

The planar antenna according to the embodiment includes theaforementioned alkali free glass according to the embodiment as a glasssubstrate. Specifically, examples of the planar antenna include a planeliquid crystal antenna having a planar shape, such as a liquid crystalantenna or a microstrip antenna (patch antenna) as an antenna excellentin directivity and receiving sensitivity. Such a liquid crystal antennais, for example, disclosed in WO 2018/016398. Such a patch antenna is,for example, disclosed in JP-T-2017-509266 or JP-A-2017-063255.

Examples

Examples is described below, but the present invention is not limited tothose examples. In the following description, Examples 1 to 12 andExamples 19 to 36 are working examples, and Examples 13 to 18 arecomparative examples.

Raw materials for respective components were prepared to obtain eachcomposition (unit: mol %) shown in Tables 1 to 6, and melted at 1,600°C. for 1 hour by use of a platinum crucible. After the melting, theobtained melt was poured onto a carbon plate, retained for 60 minutes ata temperature of the glass transition temperature +30° C., and cooleddown to room temperature (25° C.) at a rate of 1° C. per minute. Thus, asheet-like glass was obtained. The sheet-like glass was mirror-finishedto obtain a glass sheet, various physical properties of which weremeasured. Results are shown in Tables 1 to 6. In Tables 1 to 6, eachvalue in parenthesis is a calculated value, and each black designates anunmeasured item.

Methods for measuring the respective physical properties are shownbelow.

(Average Coefficient of Thermal Expansion)

Measurement was performed by use of a differential thermal expansionmeter (TMA) according to a method specified under JIS R3102 (1995). Ameasuring temperature range was set as a range of from room temperatureto 400° C. or higher, and an average coefficient of thermal expansion at50 to 350° C. was expressed by unit of 10⁻⁷/° C.

(Density)

Density of about 20 g of a glass block including no bubbles was measuredby an Archimedes method according to a method specified under JIS Z8807.

(Strain Point)

A strain point was measured by a fiber drawing method according to amethod specified under JIS R3103-2 (2001).

(Glass Transition Temperature Tg)

A glass transition temperature Tg was measured by a thermal expansionmethod according to a method specified under JIS R3103-3 (2001).

(Young's Modulus)

Young's modulus was measured for a glass 0.5 to 10 mm thick by anultrasonic method according to a method specified under JIS Z 2280.

(T₂)

Viscosity was measured by use of a rotary viscometer, and a temperatureT₂ (° C.) at which the viscosity reached 10² d·Pa·s was measuredaccording to a method specified under ASTM C 965-96.

(T₄)

Viscosity was measured by use of a rotary viscometer, and a temperatureT₄ (° C.) at which the viscosity reached 10⁴ d·Pa·s was measuredaccording to a method specified under ASTM C 965-96.

(Devitrification Temperature)

Each glass was crushed and classified into a particle size range of 2 to4 mm by use of testing sieves.

A glass cullet obtained thus was ultrasonically cleaned in isopropylalcohol for 5 minutes, washed with ion-exchanged water, then dried, putinto a dish made of platinum, and subjected to a heat treatment for 17hours in an electric furnace controlled to a fixed temperature. Thetemperature of the heat treatment was set stepwise at an interval of 10°C. After the heat treatment, the glass was extracted from the platinumdish. Maximum temperatures at which crystals were precipitated on thesurface of the glass and inside the glass and minimum temperatures atwhich no crystals were precipitated likewise were measured by use of anoptical microscope. Each of the maximum temperatures at which crystalswere deposited on the surface of the glass and inside the glass and theminimum temperatures at which no crystals were deposited likewise wasmeasured once (or twice when precipitation of crystals could not bedetermined easily). An average value of the maximum temperature at whichcrystals were deposited on the surface of the glass and the minimumtemperature at which no crystals were deposited likewise was obtainedand regarded as a glass surface devitrification temperature (T_(c)). Inthe same manner, an average value of the maximum temperature at whichcrystals were deposited inside the glass and the minimum temperature atwhich no crystals were deposited likewise was obtained and regarded as aglass internal devitrification temperature (T_(d)).

(Specific Elastic Modulus)

The Young's modulus obtained in the aforementioned procedure was dividedby the density. Thus, specific elastic modulus was obtained.

(Devitrification Viscosity)

The glass surface devitrification temperature (T_(c)) was obtained inthe aforementioned method, and viscosity of the glass at the glasssurface devitrification temperature (T_(c)) was measured and regarded asglass surface devitrification viscosity (η_(c)). In the same manner, theglass internal devitrification temperature (T_(d)) was obtained, andviscosity of the glass at the glass internal devitrification temperature(T_(d)) was measured and regarded as glass internal devitrificationviscosity (η_(d)).

TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 SiO₂ 65.2 65.2 65.2 65.265.2 65.2 Al₂O₃ 13.5 13.5 13.5 13.8 13.8 13.8 B₂O₃  1.2  1.2  1.2  1.2 1.2  1.2 MgO  9.5  9.2  8.9  8.9  9.2  8.6 CaO 10.0  9.7  9.4  9.4  9.1 9.7 SrO  0.6  1.2  1.8  1.5  1.5  1.5 BaO 0  0  0  0  0  0  RO 20.120.1 20.1 19.8 19.8 19.8 MgO/CaO  0.95  0.95  0.95  0.95  1.01  0.89Value of Expression (I)  4.27  4.23  4.20  4.21  4.23  4.19 Value ofExpression (II)  1.08  1.10  1.11  1.08  1.08  1.09 Value of Expression(III)  4.28  4.20  4.13  4.17  4.19  4.18 Average coefficient of thermal39.0 39.6 40.2 39.8 39.8 40.0 expansion (×10⁻⁷/° C.) Density (g/cm³) 2.54  2.55  2.56  2.55  2.55  2.55 Strain point (° C.) (722)   712 715  718  717  716  Glass transition temperature (° C.) 781  768  768 770  771  770  Young's modulus (GPa) 91.3 92.0 90.8 90.3 90.3 90.1 T₂ (°C.) 1611   1616   1617   1610   1610   1610   T₄ (° C.) 1276   1279  1279   1276   1276   1276   T_(c) (° C.) 1275   1275   1265   1275  1265   1275   T_(d) (° C.) <1270   <1270   <1260   <1260   <1260  1265   η_(c)(dPa · s)   10^(4.01)   10^(4.03)   10^(4.12)   10^(4.01)  10^(4.10)   10^(4.01) η_(d)(dPa · s)  >10^(4.05)   >10^(4.07)  >10^(4.16)   >10^(4.14)   >10^(4.14)  >10^(4.09) Specific elasticmodulus (MNm/kg) 35.9 36.0 35.4 35.4 35.4 35.3

TABLE 2 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 SiO₂ 64.8 64.8 63.2 63.265.2 65.2 Al₂O₃ 14.2 14.2 15.5 15.5 13.5 13.5 B₂O₃  1.2  1.2  1.2  1.2 1.2  1.2 MgO  9.0  8.6 10.0  9.2  9.5 10.1 CaO  9.0  9.4  8.3  9.1  8.8 8.2 SrO  1.8  1.8  1.8  1.8  1.8  1.8 BaO 0  0  0  0  0  0  RO 19.819.8 20.1 20.1 20.1 20.1 MgO/CaO  1.00  0.91  1.20  1.01  1.08  1.23Value of Expression (I)  4.28  4.26  4.65  4.60  4.24  4.28 Value ofExpression (II)  1.09  1.10  1.09  1.11  1.10  1.09 Value of Expression(III)  4.23  4.22  4.85  4.57  4.21  4.47 Average coefficient of thermal39.6 40.2 39.5 40.1 40.5 39.5 expansion (×10⁻⁷/° C.) Density (g/cm³) 2.56  2.56  2.58  2.58  2.56  2.56 Strain point (° C.) 715  716  720 720  710  711  Glass transition temperature (° C.) 770  772  774  775 767  767  Young's modulus (GPa) 90.0 89.7 91.5 91.6 89.8 90.3 T₂ (° C.)1611   1610   1577   1583   1613   1613   T₄ (° C.) 1277   1278   1258  1263   1276   1276   T_(c) (° C.) 1285   1275   1265   1275   1265  1265   T_(d) (° C.) <1280   <1270   <1260   <1260   <1260   <1250  η_(c)(dPa · s)   10³·⁹⁴   10^(4.02)   10^(3.94)   10^(3.90)   10^(4.09)  10^(4.09) η_(d)(dPa · s)  >10^(3.98)  >10^(4.06)  >10^(3.99) >10^(4.03)  >10^(4.13)  >10^(4.13) Specific elastic modulus (MNm/kg)35.1 35.0 35.5 35.5 35.1 35.3

TABLE 3 Ex. 13 Ex. 14 Ex. 15 Ex. 16 Ex. 17 Ex. 18 SiO₂ 66.6 65.6 65.761.9 68.4 64.3 Al₂O₃ 12.1 12.4 15.9 10.2 11.0 15.5 B₂O₃ 3.7 2.7 0 0 0 0MgO 7.6 10.9 8.0 14.2 10.0 15.7 CaO 5.2 8.4 10.4 13.7 10.6 4.5 SrO 4.8 00 0 0 0 BaO 0 0 0 0 0 0 RO 17.5 19.4 18.4 27.9 20.6 20.2 MgO/CaO 1.451.30 0.77 1.04 0.95 3.48 Value of Expression (I) 3.20 3.94 4.41 5.474.02 5.17 Value of Expression (II) 1.43 1.26 0.75 1.40 0.89 0.74 Valueof Expression (III) 4.22 4.71 4.47 5.07 3.80 37.35 Average coefficientof thermal (38) 40.0 (38) 47.0 (37) (35) expansion (×10⁻⁷/° C.) Density(g/cm³) (2.56) 2.50 2.54 2.60 (2.55) 2.55 Strain point (° C.) (698)(710) (761) (704) (731) (744) Glass transition temperature (° C.) (726)761 (811) 764 (800) (797) Young's modulus (GPa) (84.6) 89.3 92.2 92.7(89.7) 95.4 T₂ (° C.) (1647) 1615 1629 (1523) (1612) (1589) T₄ (° C.)(1297) 1272 1301 (1205) (1253) (1268) T_(c) (° C.) — (1350) — (1210) —(>1310) T_(d) (° C.) — — — — — — η_(c)(dPa · s) — — — — — — η_(d)(dPa ·s) — — — — — — Specific elastic modulus (MNm/kg) (33.0) 35.7 36.3 35.735.2 37.4

TABLE 4 Ex. 19 Ex. 20 Ex. 21 Ex. 22 Ex. 23 Ex. 24 SiO₂ 64.5 63.8 63.564.0 64.3 65.0 Al₂O₃ 14.2 14.2 16.0 15.5 15.5 12.8 B₂O₃  2.2  2.8  2.2 2.0  1.2  0.5 MgO  9.5  9.7  9.0  8.0  7.5 11.0 CaO  7.5  7.9  8.0  8.0 8.3  9.7 SrO  2.1  1.6  1.3  2.5  3.2  1.0 BaO 0  0  0  0  0  0  RO19.1 19.2 18.3 18.5 19.0 21.7 MgO/CaO  1.27  1.23  1.13  1.00  0.90 1.13 Value of Expression (I)  4.12  4.12  4.30  4.16  4.25  4.55 Valueof Expression (II)  1.21  1.32  1.14  1.16  1.08  1.06 Value ofExpression (III)  4.61  4.68  4.64  4.27  4.17  4.46 Average coefficientof thermal 38.7 (38.6) (37.3) (38.8) 39.8 (40.9) expansion (×10⁻⁷/° C.)Density (g/cm³)  2.55  (2.54)  (2.55)  (2.57)  2.59  (2.56) Strain point(° C.) 712  (707)  (725)  (723)  725  (714)  Glass transitiontemperature (° C.) 764  (764)  (785)  (784)  779  (770)  Young's modulus(GPa) 88.7 (89.1) (90.1) (88.9) 89.1 (91.7) T₂ (° C.) 1610   (1592)  (1594)   (1605)   1616   (1603)   T₄ (° C.) 1268   (1260)   (1269)  (1276)   1278   (1266)   T_(c) (° C.) 1285   (≤1280)    (≤1289)   (≤1296)    (≤1298)    (≤1286)    T_(d) (° C.) (≤1285)    (≤1280)   (≤1289)    (≤1296)    (≤1298)    (≤1286)    η_(c)(dPa · s)   10^(3.87)(≥10^(3.8))  (≥10^(3.8))  (≥10^(3.8))  (≥10^(3.8))  (≥10^(3.8)) η_(d)(dPa · s) (≥10^(3.87))  (≥10^(3.8))  (≥10^(3.8))  (≥10^(3.8)) (≥10^(3.8))  (≥10^(3.8))  Specific elastic modulus (MNm/kg) 34.7 (35.0)(35.3) (34.6) 34.4 (35.8)

TABLE 5 Ex. 25 Ex. 26 Ex. 25 Ex. 28 Ex. 29 Ex. 30 SiO₂ 65.0 64.5 65.064.8 64.3 64.3 Al₂O₃ 12.8 12.8 13.0 13.0 13.8 13.8 B₂O₃  1.2  1.8  1.5 1.8  0.5  0.5 MgO 10.0  9.3  9.0 10.0 10.1  9.6 CaO  9.0  8.6  9.5  8.4 9.3  8.8 SrO  2.0  3.0  2.0  2.0  2.0  3.0 BaO 0  0  0  0  0  0  RO21.0 20.9 20.5 20.4 21.4 21.4 MgO/CaO  1.11  1.08  0.95  1.19  1.09 1.09 Value of Expression (I)  4.29  4.16  4.16  4.18  4.60  4.55 Valueof Expression (II)  1.17  1.30  1.20  1.23  1.07  1.10 Value ofExpression (III)  4.25  4.15  4.12  4.39  4.41  4.29 Average coefficientof thermal (41.1) 41.9 (41.1) 40.6 (41.6) (42.3) expansion (×10⁻⁷/° C.)Density (g/cm³)  (2.57)  2.58  (2.56)  2.56  (2.58)  (2.60) Strain point(° C.) (709)  704  (709)  706  (722)  (722)  Glass transitiontemperature (° C.) (765)  754  (766)  758  (777)  (778)  Young's modulus(GPa) (89.9) 87.9 (89.0) 88.4 (91.2) (90.8) T₂ (° C.) (1608)   1608  (1610)   1611   (1597)   (1599)   T₄ (° C.) (1268)   1261   (1270)  1265   (1264)   (1266)   T_(c) (° C.) (≤1288)    (≤1281)    (≤1290)   1265   (≤1284)    (≤1286)    T_(d) (° C.) (≤1288)    (≤1281)   (≤1290)    (≤1265)    (≤1284)    (≤1286)    η_(c)(dPa · s) (≥10^(3.8)) (≥10^(3.8))  (≥10^(3.8))   10^(4.00) (≥10^(3.8))  (≥10^(3.8))  η_(d)(dPa· s) (≥10^(3.8))  (≥10^(3.8))  (≥10^(3.8))  (≥10^(4.00)) (≥10^(3.8)) (≥10^(3.8))  Specific elastic modulus (MNm/kg) (35.0) 34.1 (34.7) 34.6(35.3) (35.0)

TABLE 6 Ex. 31 Ex. 32 Ex 33 Ex. 34 Ex. 35 Ex. 36 SiO₂ 65.2 65.0 62.563.6 63.6 65.2 Al₂O₃ 13.8 14.5 16.0 13.0 13.0 14.0 B₂O₃  1.5  1.5  0.7 1.5  1.7  1.2 MgO  9.2  9.1 11.0 12.1  9.2  8.6 CaO  8.2  7.7  8.8  9.211.2  7.5 SrO  1.8  2.0  1.0  0.6  1.3  3.5 BaO  0.3  0.2 0  0  0  0  RO19.5 19.0 20.8 21.9 21.7 19.6 MgO/CaO  1.12  1.18  1.25  1.32  0.82 1.15 Value of Expression (I)  4.11  4.15  5.00  4.65  4.38  4.14 Valueof Expression (II)  1.11  1.08  1.02  1.23  1.32  1.11 Value ofExpression (III)  4.17  4.31  5.27  5.20  4.51  4.09 Average coefficientof thermal (39.6) (38.9) (39.7) (40.5) (42.6) (40.6) expansion (×10⁻⁷/°C.) Density (g/cm³)  (2.56)  (2.56)  (2.57)  (2.55)  (2.57)  (2.58)Strain point (° C.) (719)  (721)  (724)  (709)  (708)  (721)  Glasstransition temperature (° C.) (774)  (778)  (782)  (762)  (761)  (778) Young's modulus (GPa) (88.8) (89.0) (92.9) (91.3) (89.8) (88.8) T₂ (°C.) (1622)   (1624)   (1577)   (1573)   (1580)   (1624)   T₄ (° C.)(1279)   (1282)   (1255)   (1242)   (1245)   (1283)   T_(c) (° C.)(≤1299)    (≤1302)    (≤1275)    (≤1262)    (≤1265)    (≤1303)    T_(d)(° C.) (≤1299)    (≤1302)    (≤1275)    (≤1262)    (≤1265)    (≤1303)   η_(c)(dPa · s) (≥10^(3.8))  (≥10^(3.8))  (≥10^(3.8))  (≥10^(3.8)) (≥10^(3.8))  (≥10^(3.8))  η_(d)(dPa · s) (≥10^(3.8))  (≥10^(3.8)) (≥10^(3.8))  (≥10^(3.8))  (≥10^(4.0))  (≥10^(3.8))  Specific elasticmodulus (MNm/kg) (34.7) (34.8) (36.2) (35.8) (35.0) (34.4)

In Example 13 where Al₂O₃ was lower than 12.5%, B₂O₃ was higher than 3%,MgO was lower than 8%, CaO was lower than 6%, SrO was higher than 4%, ROwas lower than 18, and MgO/CaO was higher than 1.33, the Young's moduluswas low to be lower than 88 GPa, and T₄ was high to be higher than1,290° C. In Example 14 where Al₂O₃ was lower than 12.5%, and SrO was0%, the glass surface devitrification temperature (T_(c)) was higherthan T₄+20° C. In Example 15, Example 17 and Example 18 where the valueof Expression (II) was less than 0.95, the strain point was high to behigher than 725° C. In Example 16 where SiO₂ was lower than 62%, Al₂O₃was lower than 12.5%, MgO was higher than 13%, CaO was higher than 12%,SrO was 0%, and RO was higher than 22, the average coefficient ofthermal expansion was large to be larger than 43×10⁻⁷/° C.

Although the present invention has been described in detail withreference to its specific embodiment, it is obvious for those in the artthat various changes and modifications can be made without departingfrom the spirit and scope of the present invention. The presentapplication is based on a Japanese patent application (Japanese PatentApplication No. 2018-46960) filed on Mar. 14, 2018, the entire contentsof which are introduced by reference. In addition, all the referencescited herein are incorporated as a whole.

INDUSTRIAL APPLICABILITY

An alkali free glass according to the present invention characterized asdescribed above is suitable for applications such as a substrate for adisplay, a substrate for a photomask, a substrate for supporting anelectronic device, a substrate for an information recording medium, anda substrate for a planar antenna.

The invention claimed is:
 1. An alkali free glass having an average coefficient of thermal expansion at 50 to 350° C. of 30×10⁻⁷ to 43×10⁻⁷/° C., a Young's modulus of 88 GPa or more, a strain point of 650 to 725° C., a temperature T₄ at which a viscosity reaches 10⁴ dPa·s of 1,290° C. or lower, a glass surface devitrification temperature (T_(c)) of T₄+20° C. or lower, and a temperature T₂ at which the viscosity reaches 10² dPa·s of 1,680° C. or lower, and comprising, as represented by mol % based on oxides: 62 to 67% of SiO₂, 12.5 to 16.5% of Al₂O₃, 0 to 3% of B₂O₃, 8 to 13% of MgO, 6 to 12% of CaO, 0.5 to 4% of SrO, and 0 to 0.5% of BaO, wherein MgO+CaO+SrO+BaO is 18 to 22%, and MgO/CaO is 0.8 to 1.33.
 2. The alkali free according to claim 1, having a glass specific elastic modulus of 34 MN·m/kg or higher.
 3. The alkali free glass according to claim 1, having a density of 2.60 g/cm³ or lower.
 4. The alkali free glass according to claim 1, having a glass surface devitrification viscosity (η_(c)) of 10^(3.8) dPa·s or higher.
 5. The alkali free glass according to claim 1, having, a glass transition temperature of 730 to 790° C.
 6. The alkali free glass according to claim 1, having a value expressed by the following Expression (I) of 4.10 or more: (7.87[Al₂O₃]−8.5[B₂O₃]+11.35[MgO]+7.09[CaO]+5.52[SrO]−1.45[BaO])/[SiO₂]   Expression (I).
 7. The alkali free glass according to claim 1, having a value expressed by the following Expression (II) of 0.95 or more: (−1.02[Al₂O₃]+10.79[B₂O₃]+2.84[MgO]+4.12[CaO]+5.19[SrO]+3.16[BaO])/[SiO₂]   Expression (II)
 8. The alkali free glass according to claim 1, having a value expressed by the following Expression (III) of 5.5 or less: (8.9[Al₂O₃]+4.26[B₂O₃]+11.3[MgO]+4.54[CaO]+0.1[SrO]−9.98[BaO])×{1+([MgO]/[CaO]−1)²}/[SiO₂]  Expression (III).
 9. The alkali free glass according to claim 1, comprising 0.5% or lower of SnO₂ as represented by mol % based on oxides.
 10. The alkali free glass according to claim 1, having a β-OH value of 0.05 to 0.5 mm⁻¹.
 11. The alkali free glass according to claim 1, having a compaction of 100 ppm or lower.
 12. The alkali free glass according to claim 1, having an equivalent cooling rate of 5 to 500° C./min.
 13. The alkali free glass according to claim 1, which is a glass sheet having at least one side of 1,800 mm or longer and a thickness of 0.7 mm or less.
 14. The alkali free glass according to claim 13, which is manufactured by a float process or a fusion process.
 15. A display panel comprising the alkali free glass according to claim
 1. 16. A semiconductor device comprising the alkali free glass according to claim
 1. 17. An information recording medium comprising the alkali free glass according to claim
 1. 18. A planar antenna comprising the alkali free glass according to claim
 1. 